Hydraulic Toothed Wheel Machine

ABSTRACT

A toothed wheel machine including a housing for receiving two meshing toothed wheels. The toothed wheels are axially mounted in a sliding manner by axial surfaces between bearing bodies received in the housing, and radially by a bearing shaft received in the bearing bodies. Hydraulic mechanical forces are generated during the operation of the toothed wheel machine, an axial force component of the forces acting on each toothed wheel in the same axial direction. In order to counteract said axial force component, a pressure field is provided between at least one axial surface of one of the toothed wheels in the direction of the action of the axial force component, and the bearing body adjacent to the at least one axial surface.

The invention relates to a hydraulic toothed wheel machine in accordancewith the preamble of patent claim 1.

EP 1 291 526 A2 shows a toothed wheel machine having a housing in whichtwo intermeshing toothed wheels supported in bearing bushes or bearingbodies are arranged, the housing being closed at the ends by a first anda second housing cover respectively. The toothed wheels are eachsupported in a sliding manner axially by two axial surfaces between thebearing bodies and radially by respective bearing shafts accommodated inthe bearing bodies. During the operation of the toothed wheel machine,hydraulic and mechanical forces act on the toothed wheels along the sametoothed wheel longitudinal axis in each case. To ensure that the firstbearing body, which lies in the direction of action of the forces, isnot pushed beyond the axial surfaces of the toothed wheels, between thetoothed wheels and the first housing cover, and that only a smallsliding gap occurs between the toothed wheels and the second bearingbody, a counter-force is applied to the toothed wheels and to the firstbearing body. This counter-force is larger than the hydraulic andmechanical forces, with the result that the first bearing body ispressed against the toothed wheels, the toothed wheels are pressedagainst the second bearing body, and the second bearing body is pressedagainst the second housing cover. All the resultant forces on thebearing bodies and the toothed wheels thus act in the direction of thesecond housing cover.

The counter-force on the toothed wheels is applied via pistons acting onthe bearing shafts. The pistons are accommodated in a sliding manner,approximately coaxially with respect to the toothed wheel longitudinalaxis, in an intermediate cover arranged between the first housing coverand the housing and rest by means of a first piston end face against ashaft end face of the bearing shafts which faces in the direction of thefirst housing cover and are each subjected to pressure by way of asecond piston end face. The counter-force is applied to the firstbearing body by way of a pressure field formed between the bearing bodyand the intermediate cover.

The disadvantage with this solution is that the entire assembly ofbearing bodies and toothed wheels is pressed onto the second housingcover of the toothed wheel machine, with the result that the secondhousing cover and the housing are subjected to very high and unevenloads. The pressing together of the toothed wheels and the bearingbodies results in very high wear between the axial surfaces of thetoothed wheels and the bearing bodies. Moreover, the application of thecounter-force to the bearing shafts and the bearing bodies requires ahigh outlay in terms of apparatus, involving a large number ofcomponents.

It is the object of the present invention to provide a hydraulic toothedwheel machine which is simple in terms of the apparatus involved and isconstructed using a small number of components and exhibits low wear.

This object is achieved by a hydraulic toothed wheel machine inaccordance with the features of patent claim 1.

According to the invention, a toothed wheel machine has a housing foraccommodating two intermeshing toothed wheels. These are supported in asliding manner axially by axial surfaces between bearing bodiesaccommodated in the housing and radially by respective bearing shaftsaccommodated in the bearing bodies. During the operation of the toothedwheel machine, an axial force component of a force resulting fromhydraulic and mechanical forces arising during operation acts on eachtoothed wheel in the same axial direction. At least one pressure fieldis provided between at least one axial surface of a toothed wheel, saidaxial surface lying in the direction of action of the axial forcecomponent, and the bearing bodies adjoining the at least one axialsurface.

This solution has the advantage that a counter-force acting against theaxial force component can be applied to the toothed wheels by means ofthe pressure field, without additional components. Moreover, thepressure field reduces the axial force component acting as a contactpressure force on the toothed wheels, thereby reducing the slidingfriction between the toothed wheels and the bearing bodies lying in thedirection of action of the axial force component and minimizing wear.

The toothed wheels are preferably helically toothed.

In a preferred embodiment, a pressure field is provided between each ofthose axial surfaces of the toothed wheels which lie in the direction ofaction of the axial force component and those sliding surfaces of thebearing body which lie opposite the axial surfaces. This has theadvantage that the pressure fields can be of different sizes, making itpossible to apply different pressure forces to each toothed wheel.

The pressure fields can simply be designed as pressure pockets.

It is advantageous if the pressure pockets are introduced ascheap-to-produce pressure grooves into the sliding surfaces of thebearing body lying in the direction of action of the axial forcecomponent.

The sliding surface of the bearing body lying in the direction of actionof the axial force component preferably has introduced into it a firstpressure groove, running concentrically around a first bearing eye, anda second pressure groove, spanning a partial circle around a secondbearing eye, and different effective areas of the pressure grooves arethereby obtained.

It is advantageous if the pressure grooves are in pressure-mediumcommunication with the high pressure of the toothed wheel machine viaconnection grooves. This enables the pressure force acting in thepressure grooves to be linked to the operating conditions of the toothedwheel machine.

In another preferred embodiment, the pressure pockets are introducedinto those axial surfaces of the toothed wheels which lie in thedirection of action of the axial force component.

To enable them to be produced in a simple manner, the pressure pocketsare formed around and along a portion of the circumference of therespective bearing shafts of the toothed wheels and, as a result, theleakage gap that forms is small too.

To enable the toothed wheels to be supplied with a uniform pressure, itis advantageous if the pressure pockets are formed so as to run aroundthe respective bearing shafts of the toothed wheels.

To increase the effective area of the pressure pockets, at least onepressure pocket is preferably enlarged by tooth pocket sectionsintroduced into the tooth end faces of the teeth of the toothed wheel.

The pressure pockets can be supplied with pressure oil via the adjoiningbearing body, the pressure pockets being in pressure-mediumcommunication with the high pressure of the toothed wheel machine, forexample.

Other advantageous developments of the invention form the subject matterof further subclaims.

A number of illustrative embodiments of the invention are explained ingreater detail below with reference to schematic drawings. In thedrawings:

FIG. 1 shows a simplified illustration of a toothed wheel machine in alongitudinal section;

FIG. 2 shows a simplified illustration of an assembly of bearing bodiesand toothed wheels of the toothed wheel machine from FIG. 1, in a sideview;

FIG. 3 shows a simplified illustration of bearing bodies and toothedwheels of the toothed wheel machine according to a first illustrativeembodiment in a longitudinal section;

FIG. 4 shows a plan view of the bearing body from FIG. 3; and

FIG. 5 shows a plan view of the toothed wheels of the toothed wheelmachine according to a second illustrative embodiment.

DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS

FIG. 1 shows a hydraulic machine, embodied as a toothed wheel machine 1,according to one illustrative embodiment in a longitudinal section. Thismachine has a machine housing 2, which is closed by means of two housingcovers 4 and 6. Housing cover 6 of the toothed wheel machine 1, which ison the right in FIG. 1, is penetrated by a first bearing shaft 8, onwhich a first toothed wheel 10 is arranged within the machine housing 2.The first toothed wheel 10 is in engagement with a second toothed wheel12 by way of helical toothing 14, toothed wheel 12 being arranged on asecond bearing shaft 16 for conjoint rotation therewith. The first andsecond bearing shafts 8 and 16 are each guided in two plain bearings 18,20 and 22, 24 respectively. The plain bearings 20, 24 on the right inFIG. 1 are accommodated in a bearing body 26, and the plain bearings 18,22 on the left in FIG. 1 are accommodated in a bearing body 28. Thetoothed wheels 10 and 12 are each supported in a sliding manner in theaxial direction by respective first axial surfaces 30 and 32 on thesecond bearing body 26 (on the right in FIG. 1) and by respective secondaxial surfaces 34 and 36 on the bearing body 28 on the left. To reducefriction, sliding surfaces between the toothed wheels 10, 12 and thebearing bodies 26, 28 can be provided with an antifriction coating, suchas MoS₂, graphite or PTFE. Respective end faces 38 and 40 of the bearingbodies 26 and 28 face the housing covers 6 and 4.

The housing covers 4, 6 are aligned on the machine housing 2 by means ofcentering pins 42. A housing seal 44 is arranged between the housingcovers 4 and 6 and the machine housing 2. Respective axial field seals46 are furthermore inserted into the end faces 38 and 40 of the bearingbodies 26 and 28 to separate a high-pressure zone from a low-pressurezone of the toothed wheel machine 1. A shaft seal ring 48 seals off thefirst bearing shaft 8 where it passes through the housing cover 6 on theright in FIG. 1.

Hydraulic and mechanical forces arise during the operation of thetoothed wheel machine 1, this being illustrated schematically in detailin FIG. 2 below.

FIG. 2 shows a simplified illustration, in side view, of the assembly oftoothed wheels 10 and 12 and bearing bodies 26 and 28 in order toillustrate the hydraulic forces that arise during operation and themechanical forces that essentially act due to the helical toothing inthe toothed wheel machine 1 from FIG. 1. A force component of ahydraulic force acts in the same axial direction on both toothed wheels10, 12, toward the left in FIG. 2. In addition, a driving toothed wheel,which is the upper toothed wheel 10 in FIG. 2, is acted upon by amechanical force component of a mechanical force in the direction ofaction of the hydraulic force component, and a driven toothed wheel,which is the lower toothed wheel 12 in FIG. 2, is acted upon by amechanical force component counter to the direction of action of thehydraulic force component. The hydraulic and mechanical force componentseach produce a resultant axial force component 47, 49 in the samedirection (to the left in FIG. 2) on both toothed wheels 10, 12,although there is a difference in magnitude.

The toothed wheels 10 and 12 subjected to axial force components 47, 49are each supported by axial surfaces 34 and 36, respectively, on thebearing body 28 on the left in FIG. 2. The right-hand bearing body 26 isnot subject to the axial force components acting on the toothed wheels10, 12. To reduce wear between the toothed wheels 10, 12 and the bearingbody 28 on the left in FIG. 2, a counter-force is applied to the toothedwheels, this being indicated by dashed arrows in FIG. 2.

FIG. 3 shows a simplified illustration of the bearing bodies 26, 28 andthe toothed wheels 10, 12 according to a first illustrative embodimentof the toothed wheel machine 1 from FIG. 1 in a longitudinal section. Toapply the counter-force to the toothed wheels 10, 12, a pressure fieldis provided between those axial surfaces 34, 36 of the toothed wheels10, 12 which lie in the direction of action of the axial forcecomponents 47, and those sliding surfaces 50, 52 of the bearing body 28which lie opposite the axial surfaces 34, 36. The bearing bodies 26, 28can be of two-part construction, as illustrated in FIG. 3. The pressurefield is delimited by pressure grooves 54 and 56, respectively,introduced into the sliding surfaces 50 and 52 and by the respectiveaxial surfaces 34 and 36. Pressure forces 58, 60 acting on bearing body28 and the toothed wheels 10, 12 by virtue of the pressure field areillustrated in simplified form by double arrows in FIG. 3, with bearingbody 28 having been moved to the left to enable the pressure forces 58,60 to be illustrated more clearly. The design of the pressure grooves54, 56 can be seen in the following figure, FIG. 4.

FIG. 4 discloses the sliding surfaces 50, 52 of the spectacle-shapedbearing body 28 from FIG. 3 in a plan view. The first pressure groove 54is introduced into the sliding surface so as to run around a bearing eye62 at the top in FIG. 4. The second pressure groove 56 is formedsubstantially in the high pressure zone of the toothed wheel machine 1from FIG. 1, spanning a partial circle around a lower bearing eye 64.The pressure grooves 54, 56 are in pressure-medium communication withthe high pressure of the toothed wheel machine 1 via radial grooves 66.

The pressure forces 58, 60 are applied to the toothed wheels 10, 12 andbearing body 28 by means of the respective pressure grooves 54 and 56introduced into the sliding surfaces 50 and 52 in FIGS. 3 and 4. Thepressure forces 58, 60 counteract the axial force components 47, 49,thereby reducing the sliding friction and wear between the toothedwheels 10, 12 and bearing body 28. The size of the pressure grooves 54,56 is designed in such a way that the axial force components 47, 49applied to the toothed wheels 10, 12 are thus substantially compensatedfor by the pressure forces 58, 60, and the toothed wheels 10, 12 arethus supported approximately hydrostatically. The axial force component47 at the top in FIG. 3 is larger than the lower axial force component49, for which reason the upper pressure groove 54 from FIG. 4 isdesigned with a larger area than the lower pressure groove 56.

FIG. 5 shows a plan view of the axial surfaces 34, 36 of the toothedwheels 10, 12 in accordance with a second illustrative embodiment of thetoothed wheel machine 1 from FIG. 1. Here, the pressure field is notdelimited by pressure grooves 54, 56 introduced into bearing body 28 asin FIG. 3 but by respective pressure pockets 68 and 70 introduced intothe axial surfaces 34 and 36 of the toothed wheels 10 and 12. Thepressure pocket 70 in toothed wheel 12, said pocket being at the bottomin FIG. 5, is designed as an annular groove which is introduced aroundthe axial surface 36 between tooth end faces 72 of teeth 74 of toothedwheel 12 and an outer circumferential surface of bearing shaft 16. Inaddition to an annular groove corresponding to pressure pocket 70, thepressure pocket 68 in toothed wheel 10, said pocket being at the top inFIG. 5, has tooth pocket sections 76 introduced into the tooth end faces72, pressure pocket 68 thus being introduced into the axial surface 34over a large area. Pressure pocket 68 is then delimited radially by awall 78 running around the periphery of toothed wheel 10. The pressurepockets 68, 70 are in pressure-medium communication with the highpressure of the toothed wheel machine 1 from FIG. 1 via connectiongrooves in the adjoining bearing body 28 (see FIG. 1), for example.

By virtue of the pressure pockets 68, 70 in the toothed wheels 10, 12,the pressure forces 58, 60 from FIG. 3 are introduced in the area ofaction on bearing body 28 of the toothed wheels 10, 12 subjected toaxial force components 47, 49. Since the pressure pocket 68 at the topin FIG. 4 has a larger axial pressure application area than the lowerpressure pocket 70, the pressure force acting on the upper toothed wheel10 is greater.

As an alternative, it is conceivable for the pressure pockets 68, 70from FIG. 4 to be introduced into the toothed wheels 10, 12 in such away that they do not run around but merely span a partial circle andhave a larger radial width. This would be a way, for example, ofsimplifying manufacture and reducing the size of a leakage gap, whichwould result in smaller hydraulic losses.

The operation of the axial-gap and axial-force compensation explainedabove is independent of the construction of the bearing elements usedand can therefore be employed for all components suitable for axialsealing of toothed wheel machines. The same applies also to the type oftoothing and the parameters thereof. Such axial-gap and axial-forcecompensation can be employed both in external and internal toothed wheelmachines.

The toothed wheel machine can be used as a gear pump or motor.

The disclosure is of a toothed wheel machine having a housing foraccommodating two intermeshing toothed wheels. These are supported in asliding manner axially by axial surfaces between bearing bodiesaccommodated in the housing and radially by respective bearing shaftsaccommodated in the bearing bodies. Hydraulic and mechanical forcesarise during the operation of the toothed wheel machine, and an axialforce component of these forces acts in the same axial direction on eachtoothed wheel. To counteract this axial force component, a pressurefield is provided between at least one axial surface of a toothed wheel,said axial surface lying in the direction of action of the axial forcecomponent, and the bearing body adjoining the at least one axialsurface.

1. A toothed wheel machine having a housing for accommodating twointermeshing toothed wheels, which are supported in a sliding manneraxially by axial surfaces between bearing bodies accommodated in thehousing and radially by respective bearing shafts accommodated in thebearing bodies, in which an axial force component of a force resultingfrom hydraulic and mechanical forces arising during operation of thetoothed wheel machine acts on each toothed wheel in the same axialdirection, wherein at least one pressure field is provided between atleast one axial surface of a toothed wheel, said axial surface lying inthe direction of action of the axial force component, and the bearingbody adjoining the at least one axial surface.
 2. The toothed wheelmachine as claimed in claim 1, wherein the toothed wheels are helicallytoothed.
 3. The toothed wheel machine as claimed in claim 1 , wherein apressure field is provided between those axial surfaces of the toothedwheels which lie in the direction of action of the axial force componentand that sliding surface of the bearing body which lies opposite theaxial surfaces.
 4. The toothed wheel machine as claimed in claim 3,wherein the pressure fields have different effective areas in the axialdirection of the toothed wheels.
 5. The toothed wheel machine as claimedin claim 2, wherein the pressure fields are designed as pressurepockets.
 6. The toothed wheel machine as claimed in claim 5, wherein thepressure pockets are introduced as pressure grooves into the slidingsurfaces of the bearing body lying in the direction of action of theaxial force component.
 7. The toothed wheel machine as claimed in claim6, wherein the sliding surface of the bearing body lying in thedirection of action of the axial force component has introduced into ita first pressure groove, running concentrically around a first bearingeye, and a second pressure groove, spanning a partial circle around asecond bearing eye.
 8. The toothed wheel machine as claimed in claim 7,wherein the pressure grooves are in pressure-medium communication withthe high pressure of the toothed wheel machine via connection grooves.9. The toothed wheel machine as claimed in claim 5, wherein the pressurepockets are introduced into those axial surfaces of the toothed wheelswhich lie in the direction of action of the axial force component. 10.The toothed wheel machine as claimed in claim 9, wherein the pressurepockets are formed around and along a portion of the circumference ofthe respective bearing shafts of the toothed wheels.
 11. The toothedwheel machine as claimed in claim 9, wherein the pressure pockets areformed so as to run around the respective bearing shafts of the toothedwheels.
 12. The toothed wheel machine as claimed in claim 11, wherein atleast one pressure pocket is enlarged by tooth pocket sectionsintroduced into tooth end faces of the teeth of toothed wheel.
 13. Thetoothed wheel machine as claimed in claim 10, wherein the pressurepockets are supplied with pressure oil via the adjoining bearing body.